How to raise a validation error in Rails after save

gistfile1.rb

# This probably isn't a good thing to want to do, but it came up for me,
# so in the spirit of helping others with weird problems (and because this
# seems to be documented almost nowhere):

after_save do
  
  if some_failing_condition
    errors.add(:something, "some failure happened.")
    raise ActiveRecord::RecordInvalid.new(self)
  end
  
end

THANKS!

Yep, still helpful in 2019 :) Thanks!

This approach is also really useful in situations where you want to use ActiveModel::Dirty tracking, but also ensure that it's a valid update before progressing:

user.transaction do
  user.assign_attributes(user_params)
  raise ActiveRecord::RecordInvalid.new(user) if user.invalid?

  if user.email_changed?
    # Do something
  end
end

raises Class: RuboCop::Cop::Style::RaiseArgs cop with rubocop. Any hints?

Hi!, this is helpfull, but I was wondering how would you rollback the saved record, after that?

Still helpful in October 2020. We were on Rails 6 and we thought "oh, but it's all ActiveRelation now" but nope, ActiveRelation inherits from ActiveRecord::Base, and this is still the correct error class. Thank you!

raises Class: RuboCop::Cop::Style::RaiseArgs cop with rubocop. Any hints?

raise ActiveRecord::RecordInvalid, user if user.invalid? and no rubocop error

Thanks!!